Fasting Blood Glucose Levels for diabetic and Healthy person

What is normal blood sugar level fasting?
Assessed to diagnose or monitor Type 1 and 2 diabetes.
Adult fasting sugar level between 70–105 mg/dL; SI units: 3.9–5.8 mmol/L,
Some labs may set normal FBG levels to be 75 – 110 mg/dl
Blood glucose Child levels at 2 years old 60–100 mg/dL
Fasting Blood Glucose Critical Levels 50 and lower or 400 mg/dL and higher, and considered diagnostic without further tests

Blood Glucose levels interpretation:
Remember that:
Type one diabetes is insulin-dependent while type 2 diabetes is insulin-independent.
High Fasting Glucose is hyperglycemia in medical terms, low FBG is Hypoglycemia in medicine.
Prolonged high levels of Blood glucose can produce heart disease, kidney disease, blindness, along with low immunity infections such as fungi infection
More about high glucose levels

Diagnostic Fasting blood glucose is levels higher than 125 mg/dl, diagnose as diabetic without GTT or HbA1C tests, so that an elevated fasting blood glucose level above 125 mg/dL on at least two occasions typically indicates diabetes.
Also the first diagnosis is diabetes symptoms such as increased thirst or hunger, frequent urination, weight loss, blurred vision, which require only one test to confirm that patient is diabetic.

Glucose levels in blood differ from case to case and from disease to disease.
According to WHO guidelines, each medical laboratory must set their controls and standard values to before measuring sugar levels in patient blood.

Normal fasting sugar level for healthy person
Normal level of blood glucose for non-diabetic person should be a value between 70-110 mg/dl (international measurement SI unit).

Normal glucose in blood for diabetic person is something going higher than 110 mg/dl, however according to WHO guidelines the blood sugar values greater than 126 mg/dl after 6 hours fasting is considered diabetes melitus patient..

Prediabetic Glucose levels at fasting
6 – 8 hours fasting Glucose levels lies between 100-125 mg/dl is so called insulin resistant person or the patient is prediabetic and should control their diet and mild treatment.

in such case insulin levels in blood may be low due to abnormally functioning pancreas or normal insulin level due to other circumstances

When fasting blood glucose lies in that suspicious range, other confirmation tests must be done to reassure that glucose level is normal or tend to be high or glucose is good controlled.

Confirmation Blood tests will tell you how well you are managing your diabetes, including oral glucose tolerance test (shortcut OGTT or GTT), Postprandial glucose test and HbA1C blood test.

Postprandial Glucose test
may be called meal tolerance test (MTT) or postprandial blood glucose test (PPG), measure glucose level in blood 2h post lunch.
2h PP-glucose level is made by take a blood sample after a medium meal by 2 hours, sugar level measured in blood, 140 mg/dl is normal PPG but higher values with FBG level higher than 126 mg/dl does confirm diabetes millitus results type1 or 2.

Glucose Tolerance Test,
Standard Oral, require overnight fasting from food not water
Fasting normal level is 126 mg/dL; SI units: 7 mmol/L
After 2-hr normal level: 200 mg/dL; SI units 1.1 mmol/L
Normal 140 mg/dL,
Levels indicate impaired glucose tolerance are 140-199 mg/dL,
Diabetes level is values equal to or higher than 200mg/dL

Blood glucose levels are assessed twice. The first is a fasting sample, the second sample is taken 2 hr after ingestion of 75 g of glucose. Samples may be assessed at other times as well, in lab and for pregnant women GTT test may be taken as 5 samples first one after 6 hours or more fasting and one every 30 min of taking 75 g glucose solution, then the curve is made to be certain that glucose values for a patient lies between the accepted levels.

Useful for screening for prediabetes and used specially for gestational diabetes but usually unnecessary for diagnosing diabetes as fasting blood glucose 126 mg/dL or a random blood glucose level 200 mg/dL is usually considered diagnostic, Also GTT test results is affected by carbohydrates diet.
For such reasons, physicians not usually request a measurement of GTT test except for pregnant.

False FBG positive/negative results:

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Do not hesitate to repeat he glucose test is the results not correlated with your symptoms or with other tests.
Failed to fast 6 – 8 hours prior to glucose testing due to drinking coffee or such sweet drinks or foods which raise Fasting sugar levels in patients blood.
Higher than 8 hours fasting may be falsely reduce fasting glucose level when tested.
Some foods affect BG levels so that beware of them such as:
Lime and lemon juice delay the digestion of starches as does vinegar, hence they reduces postprandial BG by 10-20 points.
Cinnamon also cause BG to fluctuate
Alcohols do lower blood glucose value very much
Medication makes abnormal FBG results:
corticosteroids, birth control bills or oral contraceptives, a seizure medication such as, thiazide diuretics which often used to treat high blood pressure, Vitamin C, and aspirin
Muscular Exercise consume blood sugar higher 20 times than normal body status, therefore FBG show lower than expected.
More about False results
How carbohydrates affect FBG levels?
Carbohydrate intake lowering he Fasting blood glucose level as the chart show that
low fasting glucose about 80 mg/dl can be a result of high-carb diet, 20% carb diet can lower glucose at fasting to an intermediate fasting glucose level about 95 mg/dl, and very low-carb diet can enhance blood sugar concentration and show in blood test as high fasting glucose about 105 mg/dl.

Real examples of Fasting glucose levels:

My fasting blood glucose is normal 90 but postprandial glucose is high 160, what does that means?
It means you are diabetic and doctor should adjust your sugar level soon

My FBG is low 60 mg/dl after 8 hours fasting?
You are on carb. diet for long time before taking the test or did exercises or took glucose pills prior to fasting, recommended to repeat fasting test with standard requirements to ensure results is ok, if still low fasting glucose level then consult a specialist immediately.

Blood work show fasting sugar 200 mg/dl and ++ urine glucose, what does that means?
Abnormal Blood Fasting sugar and urine glucose is high which confirm the blood result and therefor you are certainly diabetic without any further confirmation tests and must feel like diabetic people fast hunger and abnormal urination..etc, medication must start promptly.

Lab test results come up with high glucose after fasting 155 while low glucose 120 post lunch, does that make sense?
Unusual fasting blood glucose level, be certain that, you didn’t take medication after the first fasting sample, didn’t exerted prior to testing, your usual diet is not carbs, after all of that I recommend to re
test glucose test with natural conditions.

Pregnant woman have FBG 97 but + glucose in urine, am I diabetic?
Pregnant women are vulnerable to get diabetic and abnormal blood levels of glucose, normal glucose in blood but a little high in urine is frequently seen in pregnant and cause no harm, your gynecologist know that.

More Patient case studies explained later
Diabetic Person should watch their diet. No bread, potato’s, or pasta, in order to cut out the carbs. Eat meat and veggies to enhance your body. 

I don not know what your FBG level is, you can put your result in comments to get interpreted, or send them privately to me, Ask for my email.

Dr.Megan Ralf

A Medical laboratory Scientist who devoted his life to medical and laboratory sciences, writes his everyday expertise dealing with various pathological conditions through laboratory diagnosis of different body fluids, also participating in many workshops for first aids, infection control, and urgent care. Also Dr Megan Ralf coaching many medical teams.

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